Circuit breakers



Nov. 8, 1960 c. K. sTRoBEL ETAL 2,959,651

CIRCUIT 'BREAKERS Filed oct. 24, 1957 United States Patent F CIRCUITBREAKERS Charles K. Strobel, Pittsburgh, and Guy F. Conner, WestMifflin, Pa., assignors to Robertshaw-Fulton Controls Company, Richmond,Va., a corporation of Delaware Filed (let. 24, 1957, Ser. No. 692,093

8 Claims. (Cl. 20G-122) This invention relates to circuit breakers andmore particularly to the type of circuit breaker for use in screw typefuse sockets.

For a circuit breaker to be truly interchangeable with a screw typefuse, it is necessary that it be of such dimension that it can beinserted in the standard boxes and panel boards encountered incommercial practice. Since most of these boxes and panel boards areshallow, this problem has not been successfully solved.

It is, therefore, an object of this invention to reduce the overallheight of a circuit breaker by greatly reducing the length of movementof its operating means while retaining its effectiveness.

Another object of this invention is to open and close a pair of contactsin such a manner that a minimum length of movement is required by theoperating elements etfectuating this action.

A further object of this invention is to increase the force whileshortening the length of movement of a circuit breaker operating means.

It is a further object of this invention to utilize a heat motor tooperate a circuit breaker.

In particular, the invention relates to a circuit breaker of the typehaving a pair of contacts operable to an open and closed position andnormally held in a closed position by a latch. A heat motor responsiveto the heat set up by the conveyed current automatically unlatches thecontacts to an open position upon occurrence of a predetermined current,while a reset device is manually operable to relatch the contacts to aclosed position.

The foregoing and all other features, objects, and advantages willbecome apparent from the following description taken in connection withthe accompanying drawing, wherein:

Fig. 1 is a vertical cross-section of the circuit breaker of thisinvention showing the contacts in their closed position;

Fig. 2 is a view similar to Fig. l showing the contacts in their openposition;

Fig. 3 is a vertical cross-section of a modification of a circuitbreaker showing the contacts in their closed position; and

Fig. 4 is a view similar to Fig. 3 showing the contacts in their openposition.

Referring more particularly to Fig. 1, there is shown a generallycylindrical housing of insulating material, indicated generally at 1i).Centrally disposed bores of different diameters are provided at oppositeends of the housing, defining a shoulder portion 12 at their points ofjuncture. A cylindrical body 14, corresponding in length and diametersto the internal dimensions of the body 1l), is adapted to be slidablyinserted into body through the larger diameter end thereof. The shoulderportion 12 engages a mating shoulder of the body 14 to prevent axialmovement thereof in one direction. A cover member 16 of insulatingmaterial is `sealed to body 10, by any suitable means, at the larger2,959,651 Patented Nov. 8, 1960 diameter end thereof to prevent axialmovement of the body 14 in the other direction.

The body 14 consists of an upper cup-shaped metal shell 18 and a lowercup-shaped shell 20 of insulating material which may be fastenedtogether by any suitable means (not shown) to form a unitary structurecontaining the operating components of this device. The interior of thelarge diameter shell 18 forms a switch chamber 22 with a centrallydisposed aperture 24 in one end thereof. The smaller diameter shell 20is centrally located relative to the switch chamber 22 and the interiorthereof forms heat motor chamber 26. A hole 28 is bored in the smalldiameter shell 2i) in axial alignment with aperture 24. Positioned in agroove 30, deiined in aperture 24, is a ilat circular washer-shapedretaining member 32 in axial alignment with hole 28.

A cylindrical heat motor body 34 with a reduced diameter at one end, isdisposed axially in chamber 26 with both ends extending therefrom; thereduced diameter end extends into chamber 22 through retaining member 32and the other end extends outwardly of the shell 20 through hole 28. Theheat motor body 34 is fastened in hole 28 by any suitable means (notshown) to prevent any movement thereof. A heat motor for purposes ofthis description comprises the heat motor body 34, a heating coil 36,and a thermally responsive ram 38. It may be of any standard typewherein the body 34 contains a conned ram 33 movable between an activeand an inactive position in accordance with temperature variations ofthe heat motor body 34 as determined by the magnitude of current owingin coil 36.

Switch means are located in the switch chamber 22 and comprise a pair ofcontacts 4b, 42 and resilient member 44. Contact 40 is shown fastened toa lateral wall of the chamber 22 and insulated therefrom by dielectricmaterial 46. Contact 42 is fastened to a resilient member 44 andinsulated therefrom by dielectric material 48. The member 44 isfastened, as by a rivet, to the lateral wall of the chamber 22 andbiases the contact 42 away from engagement with contact 4Q. A por tionof the length of member 44 is shown (Figs. l and 2) as lying along thelateral wall of the chamber 22 and a portion lying parallel to andspaced from the lateral wall of chamber 22. A resilient latch member 50is fastened to the lateral wall of chamber 22 diametrically opposite thecontacts 40, 42 and extends outwardly from the lateral Wall toward theresilient member 44 for engagement therewith. During normal operation,the latch 50 engages resilient member 44 and, against the bias thereof,holds the contacts 40, 42 in a closed position. As illustrated in Fig.1, the latch 5@ rests upon ram 38 in its inactive position with thecontacts 40, 42 and the latch Si) in their normal operating position.

A reset member, indicated generally at 52, is operative to return thelatch 5t) and the contacts 4t), 42 to their normal operating positions.An elongated stem 54 slidably lits in an aperture 56 bored in the largerdiameter shell 18 and the cover member 16. An enlarged diameter head 58is centrally located exterior to housing 10 at one end of stem S4 toprovide means for manual engagement of member 52. A spring 60 surroundsa portion of stem 54 and is mounted in compression between cover 16 andthe undersurface of the head 58 to normally bias member 52 in adirection away from engagement with the latch 50. An enlarged diametercam member 62, which can be made integral with stem 54, is located nearthe other end of stem 54 within chamber 22. The surface of the cam 62tapers increasingly and radially outward from its smaller circumferencenearest the end of stem 54 to its larger circumference furthest awayfrom the end of stem 54. Cooperable with cam 62 is a cam follower 64which is fixed to resilient means 44 on the portion thereof -which lieson the lateral surface of chamber 22.

A shell-like fuse base member 66 is fastened to one end and a portion ofthe lateral surface of the exterior of housing lll. Base 66 adapts thiscircuit breaker to be threaded into a fuse socket and make electricalcontact with one terminal thereof. A connecting wire 68 is providedbetween the shell 66 and the contact 40. A terminal 7i), adapted to makeelectrical contact with a corresponding contact of a fuse socket, isprovided on the extending portion of the heat motor body 34. One end ofthe coil 36 is connected to terminal 70 and the other end is connectedto contact 42. In normal operation, this device is threaded into andmakes electrical contact with a fuse socket to which is connected anexternal circuit to be protected,

In the use of the circuit breaker as thus far described, the currentwill pass from terminal 70 through coil 36, contact 42, contact 4C, andwire 63 to screw base 66. A transient overload, that is, one of the typenot injurious to the externally connected circuit, will not heat theheat motor sufriciently to change the relation shown in Fig. 1. Upon asufficiently sustained overload however, ram 38 will be moved axiallyfrom its inactive position to its active position. With latch 5unormally resting against ram 3S, the axial movement of the ram will movethe latch to the limit of the rams travel. This length of travel is suchthat the latch Sil will be moved to its inoperative position disengagingresilient member 44, as illustrated in Fig. 2, and allowing the contacts40 and 42 to open with a snap action under the bias of resilient member44. By reason of this snap action, the contacts Will be parted sorapidly that no arc will be maintained and the circuit will be sharplyinterrupted With contacts 4i? and 42 in their open positions, thecurrent will cease to ilow in the external circuit and in the coil 36.With no current flow in the coil 36, the ram 38 will move axially to itsinactive position away from engagement with the latch Sil and the latchand contacts will remain in their inoperative positions illustrated inFig. 2 until returned to their normal operative positions by resetmember 21. Manual engagement of head 58 causes cam member 62 to slidablyengage cam member 64 causing movement of the resilient means 44 andcontact 42 toward contact 49 to close contacts 40, 42. Simultaneouslywith the engagement of the two cam members 62 and 64, the end of sternS4 located in the interior of chamber 22 engages latch Sil to move it toits normal operative position engaging resilient member 44 to holdcontacts 40 and 42 in their closed position. Travel of the latch 50 toits normal position and the travel of the member 52 in that direction islimited by the ram 38 in its inactive position. Travel of the member 52in the other direction is limited by the enlarged diameter of the cammember 62.

The ram will remain in its active position after movement thereto untilthe heat motor cools sufficiently to allow it to return to its inactiveposition. Accordingly, it would be impossible to reset the circuitbreaker prematurely. Thus, adequate time is afforded for the wires ofthe previously overloaded circuit to cool down before the circuit can bereclosed.

In the modification illustrated in Fig. 3, the housing 72 has centrallydisposed bores of dilferent diameters at its opposite ends. The bores donot communicate, as in the Fig. l embodiment, but instead a divider 74made integral with housing 7?; is provided to separate the interior ofthe housing 72 into two chambers. rl`he interior of the larger diameterchamber constitutes the switch chamber 22.

Slidably inserted into the smaller diameter chamber is an integral unitcomprising the heat motor body 34, insulating shell 76, and heating coil36. The, insulating shell 76 is rigidly fastened to the wall of thesmaller diameter chamber by any suitable means (not shown). The heatmotor shown in this embodiment functions in substantially the samemanner as the one shown in the Fig. l embodiment. The thermallyresponsive means are, however, composed of a bellows 78 and a ram member79 movable therewith in response to the temperature variations of theheat motor body 34 as determined by the magnitude of current tiowing incoil 36. The ram 79 is disposed axially in an aperture 80 provided individer 74 and freely slidable therein when moved between its active andinactive positions in response to actuation of the bellows 78.

A cylindrical reset member 82 comprises different diameters at itsopposite ends, separated by a shoulder portion 84 at their point ofjuncture. The smaller diameter portion of the reset member 82 extendsoutwardly of the chamber 22 through an aperture 86, bored in a cover 88,in axial alignment with aperture 80. The extending portion of the resetmember 82 is manually engageable exterior to the circuit breaker and isfreely slidable in aperture 86. One end of ram 79 is received within anenlarged diameter bore provided in the larger diameter end of member8.2. Integral with the lateral surface of the larger diameter portion ofreset member 82 is an axially disposed cam member 92.

Upon manual engagement of reset member 82 the surface of the cam member92 engages that portion of resilient member 44 lying parallel to butspaced from the lateral surface of chamber 22 and urges member 44 andcontact 42.V toward contact 40. Engagement of the resilient means 44 bythe extreme circumferential edge of cam92 will latch the contacts 4i)and 42 in their closed positions and further movement thereafter of themember yS2 will move the cam 92 along the resilient member 44 untillimited by the bellows 78 coming -to rest against the bottom of heatmotor body 34, as illustrated in Fig. 3. A predetermined over-current inthe circuit connected externally to the fuse socket will cause the heat`motor to move ram 79 to an active position so that member 82 and thelatching cam 92 are moved to an inoperative position. Contacts 40 and 42will open, as illustrated in Fig. 4, when cam 92 disengages member 44and motion of the member 82 in this direction will be limited by theshoulder portion S4.

While the invention has been shown incorporated in a fuse plug, it willbe understood that the construction could be readily incorporated in anydesired size or shape of casing and although specific embodiments of theinvention have been shown and described, it will be apparent that manymodifications may be made by those skilled in the art. Suchmodifications may be made in the details of construction and arrangementof parts without departing from the scope of the invention as set forthin the appended claims.

We claim:

1. In a circuit breaker, the combination comprising a housing ofinsulating material, a shell of electrical conducting material on saidhousing, a fixed contact mounted in said housing and connected to saidshell, a spring contact arm having one end iixedly mounted in saidhousing and a free end movable therein, a movable contact mounted on thefree end of said arm and being engageable with said fixed contact,latching means engaging said arm and being movable between operative andinoperative positions, a heating element electrically connected to saidmovable contact, thermally responsive means mounted in said housing andbeing operable between active and inactive positions in response to saidheating element, an axially movable member between said thermallyresponsive means and said latching means for moving said latching meansto its inoperative position when said thermally responsive means isoperated to its active position in response to a predeterminedtemperature condition of said heating element, and manually operablemeans for moving said latch means to its operative position uponmovement of said thermally responsive means to its inactive position.y

2. In a circuit breaker; the combination comprising a housing ofinsulating material; a shell of electrical conducting material on saidhousing; a iixed contact mounted in said housing and connected to saidshell; a spring contact arm having one end xedly mounted in said housingand a free end movable therein; a movable contact mounted on the freeend of said arm and being engagee able with said fixed contact; latchingmeans engageable with said `arm yand being movable between operative andinoperative positions; a heating element electrically connected to saidmovable contact; thermally responsive means mounted in said housing andbeing movable be'- tween active and inactive positions in response tosaid heating element; -an operable connection between said thermallyresponsive means and said latching means to move the same to itsinoperative position when said thermally responsive means is moved tothe active position in response to a predetermined temperature conditionof said heating element; a manually operable reset means having oneportion engaging said spring contact arm to move said movable contactinto engagement with said Xed contact and having another portionengaging and moving said latch means into its operative position whensaid thermally responsive means returns to the inactive position; andmeans normally biasing said reset means away from engagement with saidlatch means and said spring contact arm.

3. In a circuit breaker, the combination comprising a housing ofinsulating material, a shell of electrical conducting material on saidhousing, a pair of mating contacts disposed in said housing -andconnected to said shell, a resilient contact arm normally biased toseparate said contacts, latching means engaging said arm and beingmovable between operative and inoperative positions and engaging saidcontact arm when in its operative position to retain said contacts inmating engagement, a heating element electrically connected to saidmovable contact, thermally responsive means mounted in said housing andbeing operable in response to said heating element, a ram memberoperable between an active and an inactive position and engageable withsaid latching means when in its active position to move the same to itsinoperative position in response to a predetermined temperaturecondition of said heating element, a manually operable reset meansmovable when said ram member is in the inactive position to engagesimultaneously the said resilient contact arm to move said con-tactsinto their engaged position `and said latching means for movementthereof into its operative position, and means normally biasing saidreset means away from engagement with said latch means and said springcontact arm.

4. In a circuit breaker, the combination comprising a housing ofinsulating material, a shell of electrical conducting material on saidhousing, a heat motor carried by said housing and having a terminal basecooperable with said shell for electrically connecting the breaker inthe circuit, said heat motor including an axially movable memberresponsive to an overtemperature condition of said heat motor foractuation to an operative position, electrical heating means for saidheat motor and being subject to overload to produce said overtemperaturecondition, a pair of separable contacts in said housing and engageablefor completing a circuit `through said shell and said terminal to saidheating means, resilient means normally biasing one of said contacts toa disengaged position, and a second axially movable member carried bysaid housing for manual actuation to an operative position in opposedrelation to the first said axially movable member, said second memberincluding ya latching element operatively engageable with said resilientmeans for establishing said contact engagement in the absence of saidovertemperature condition.

5. The combination recited in claim 4 wherein said first and secondmembers are carried in axial alignment from opposite ends of saidhousing, and said resilient means comprises a yieldable plate having afree end por tion extending substantially parallel with an inner wall ofsaid housing for slidable engagement with said latching element.

6. The combination recited in claim 5 wherein said housing defines aswitch chamber and a heat motor chamber in overlying relationship, saidlatching element comprising a yieldable bar supported at one end in saidswitch chamber and having a free end engaging said free end portion,said rst and second members being operative on opposite sides of saidbar.

7. The combination recited in claim 6 wherein said second member and aninner wall of said switch chamber have interengaging members effectiveupon said manual actuation of said second member for overcoming the biasof said resilient means to cause said contact engagement.

8. The combination recited in claim 5 wherein said latching elementcomprises an abutment on said second member movable axially therewithinto and out of engagement with said free end portion.

References Cited in the tile of this patent UNITED STATES PATENTS1,445,207 Foltz Feb. 13, 1923 2,043,470 Dyer et al June 9, 19362,057,093 Geisslinger Oct. 13, 1936 2,073,103 Hodgkins Mar. 9, 19372,148,880 Sattler Feb. 28, 1939 2,162,343 Brace June 13, 1939 2,202,550Elkin May 28, 1940 2,318,076 Johns May 4, 1943 2,491,032 Burke Dec. 13,1949 2,595,846 Hall et al May 6, 1952 2,669,625 Roberts et al Feb. 16,1954 2,789,180 Cox Apr. 6, 1957 FOREIGN PATENTS 159,478 Great BritainAug. 25, 1922

